Copying UVs from a high to low poly model?
You can try the "transfer data" tool (the modifier also works, sometimes...).  

Here is a "HD" mesh with UV and texture  

  

And here is a LD mesh without UV
  

Select your LD mesh first and then add your HD mesh to the selection with Shift+Right click. The last selected object is considered as active.
Open the tools bar with T. In the Tool tab, scroll to Edit and click on "Data Transfer: DATA" button

Select "UV" in the menu.

Choose the options that looks the best.

The UV has been transferred from the HD mesh to LD mesh.

Now you can create the seams from UV islands from the UV menu in image editor.
  

The LD mesh has Seams, UV and the texture is OK